Fine filters are frequently used in motor vehicles today, in particular with two-stage fuel feed units, and are known in practice. As a rule, the first stage of the fuel feed unit feeds fuel from a fuel tank via a preliminary filter into the upper region of the surge chamber. The second stage of the fuel feed unit feeds the fuel from the lower region of the surge chamber to an internal combustion engine of the motor vehicle. In this case, the fine filter is arranged in the central region of the surge chamber and has a housing which has the fuel flowing axially through it and has the filter element arranged in it. The disadvantage of the conventional fine filter is that it is very costly to construct and requires a large amount of space. The filter therefore requires a very large surge chamber. This results in a very cost-intensive construction of the surge chamber and of the fine filter.
In one construction, the fine filter annularly surrounds the fuel feed unit and is fastened to the bottom of the surge chamber. This fine filter has small dimensions, but is not able to filter the fuel in a sufficient and long-lasting manner. In order to avoid rapid clogging of the fine filter with dirt particles, the filter element therefore has a mesh width of 40-80 μm as a rule.